#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
//https://www.luogu.com.cn/problem/P1435
using namespace std;
const int N = 1010;
int f[N][N];
string s;
int main()
{
	cin >> s;
	int n = s.size();
	s = " " + s;

	for (int len = 2; len <= n; ++len)
	{
		for (int i = 1; i + len - 1 <= n; ++i)
		{
			int j = i + len - 1;
			if (s[i] == s[j])
			{
				f[i][j] = f[i + 1][j - 1];
			}
			else
			{
				f[i][j] = min(f[i + 1][j], f[i][j - 1]) + 1;
			}
		}
	}

	cout << f[1][n] << endl;




	return 0;
}